Sharply rising cases of some sexually transmitted diseases — including a 26% rise in new syphilis infections reported last year — are prompting U.S. health officials to call for new prevention and treatment efforts. “It is imperative that we … work to rebuild, innovate, and expand (STD) prevention in the U.S.,” said Dr. Leandro Mena of the U.S. Centers for Disease Control and Prevention in a speech Monday at a medical conference on sexually transmitted diseases.